The present invention relates to a stable pharmaceutical composition for injection containing docetaxel and a method of preparing the same. More particularly, the present invention relates to a pharmaceutical composition for injection containing docetaxel having better storage stability than conventional medications, which is prepared by dissolving docetaxel, a water-insoluble compound, in distilled water after mixing it with cyclodextrin (CD) and a water-soluble polymer such as hydroxypropyl methylcellulose (HPMC), polyethylene glycol (PEG) or polyvinylpyrrolidone (PVP) and lyophilizing the mixture, and a method of preparing the same.